Designing, retrofitting hospitals during COVID: Electrical, power and lighting
While COVID-19 has changed many aspects in a health care facility, some things remain identical. Understand how to design electrical, power and lighting systems
- Luis Alvarez Colon, PE, Associate, Page, Austin, Texas
- Allison Graves, PE, Principal, RTM Engineering Consultants, Chicago
- Jeff Hankin, PE, LEED AP, Senior Principal, Stantec, San Diego
- Reed Paitich, PE, Associate, Wold Architects and Engineers, Saint Paul, Minn.
- Keith D. Prata, PE, LEED AP BD+C, Mechanical Department Manager, Bala Consulting Engineers, Boston
- Donald R. Stevens, CHFM, CHC, Director – Health Care Facilities, Lockwood Andrews & Newnam Inc. (LAN), Austin, Texas
Are there any issues unique to designing electrical/power systems for these types of facilities?
Donald R. Stevens: Reliability and redundancy is key. Some hospital systems are adding tertiary power systems based on renewable energy sources to reduce carbon footprint and energy costs.
Luis Alvarez Colon: The essential branches are unique for health care buildings. These branches are in place to maintain power to power and lighting to critical spaces when an outrage occurs. Additional unique designs include isolated power systems that prevent electric shock to patients who are susceptible to leakage current normally implemented in the operating rooms. The essential branches need to be identified and routed through the building per NEC 517.31.
In the aftermath of several recent severe weather events, owners of such projects are increasingly interested in electrical/power resiliency features. How are you meeting these demands?
Donald R. Stevens: In our recent projects, it’s been mostly about hardening generator locations and distribution equipment and pathways. In Houston, where we have worked on numerous projects, flooding is our biggest threat so elevating equipment 20 to 25 feet above mean sea level is the first step. Hurricane force wind resistant structures are also required here.
Reed Paitich: Air conditioning is vital in keeping the residents of care centers comfortable especially during the summer months. Taking this large load into account is important. An outdoor location allows a properly sized generator that doesn’t take up valuable floor space. A portable generator docking station to satisfy NEC 700 is also located nearby. Typically, the docking station is sized for the entire building load instead of just life safety to address concerns of a primary generator failure during severe weather. Using multiple transfer switches or bypass isolation in the equipment branch is another strategy to provide increased resiliency.
Luis Alvarez Colon: In our designs, we try to maintain several paths to the most critical spaces such as operating room. For example, when we design an OR we normally have a minimum of two isolation panels in each room and we power each of these panels from the critical branch from different automatic transfer switches if possible. This way, we have some redundancy into the same space if one of the critical branches is not working, we still have another one to support the space. The health care buildings need to have two independent sources of power, a normal that supplies the whole system and another for alternate sources (essential systems) for use when normal power is interrupted. Typically, this alternate source is provided by a diesel generator. It is common that the medical equipment used to treat the patients will have integrated batteries so if there is a power outage the equipment will not turn off but rather keep working until the alternate source is online. The batteries work as a bridge between the power outrage and the time that the generator is online, typically this takes 10 seconds or less.
What are some of the challenges when designing high-voltage power systems in hospitals, health care facilities and medical campus projects?
Donald R. Stevens: The biggest problem with medium-voltage distribution systems is maintenance. The electrical staff has to be trained specifically on 4,160-volt equipment, for example, which is different from what they’re used to with 480-volt gear. Alternatively, some institutions contract out medium voltage work which is an additional expense and management chore. Routine testing and certification require different equipment as well.
What types of unusual standby, emergency or backup power systems have you specified for such facilities? Describe the project.
Donald R. Stevens: Co-generation is becoming more widely used. We’ve seen several clients use gas-fired turbines and heat recovery steam generators for process steam and to drive steam-powered chillers. If the overall system efficiency is good, utility costs go down and redundancy is achieved.
Luis Alvarez Colon: The source for the emergency or standby power is not unusual, however the distribution of the emergency power is. The distribution is broken down into three branches (each with its own transfer switch if the system is above 150 kVA, if not then one transfer switch is allowed). The three branches are essential power systems and include the life safety, critical and equipment branches. With these different branches, the emergency switchboard/switchgear has to be designed so that the life safety and critical branch feeders have their own section in the piece of equipment.
Per NFPA 110, any Level 1 system (systems where failure of the equipment to perform could result in loss of human life or serious injury) or emergency power supply system (emergency gear, ATS etc.) shall not be installed in the same room with the normal service equipment, where the service equipment is rated over 150 volts to ground and equal to or greater than 1,000 amperes. This requirement prompts the need to separate these systems within the building. Also, within NFPA 110, if the emergency power supply, such as the generators, is within the building then a two-hour rated room for this equipment needs to be in place.
What are some key differences in electrical, lighting and power systems you might incorporate in this kind of facility, compared to other projects?
Luis Alvarez Colon: Power: Patient bed located in critical spaces need to be supplied by two branch circuits: one from the normal and one from the critical or both from critical branch but from panels that are fed by two different transfer switches.
Life safety power: Loads that will be connected to the life safety power are more specific in health care than in other projects. In office buildings, your life safety will be connecting egress lighting as well as the fire alarm system. In health care projects, you add medical gas alarms, automatic doors on the egress path, hospital communications, among other elements outlined in NEC 517.33.
Critical power: This unique branch in health care facilities is a system that supplies power to illumination, fixed equipment, select receptacles and select power circuits serving areas and functions related to patient care.
How does your team work with the architect, owner’s rep and other project team members so the electrical/power systems are flexible and sustainable?
Luis Alvarez Colon: During kick-off meetings, we sit down with the owner and ask the important questions about the spaces and the indented uses. Once that is sorted out, we sit down and create a process with the architect to establish how we are going to provide the design intent for those spaces. There is a lot of coordination in health care buildings due to the amount of equipment and devices from different systems especially in critical care spaces such as nurse call, data, monitors and fixed equipment related directly to the space (such as an infant warmer in a labor and delivery room).
A coordinated design effort is very important because of the variety of systems and how it all comes together. For example, the patient headwall in which the systems are mounted are pre-manufactured.
What kind of lighting designs have you incorporated into a health care project, either for energy efficiency or to increase the occupant’s experience?
Luis Alvarez Colon: In patient rooms, we have implemented circadian lighting to support human health by minimizing the effect of electric light on the natural circadian rhythm. The concept of circadian lighting is to follow the human circadian rhythm, the 24-horur cycles that are part of the body’s internal clock, running in the background to carry out essential functions and processes. This circadian rhythm is mainly controlled through the eyes telling the body when it’s daytime and nighttime. There are several ways we can achieve this:
- Intensity tuning: With a fixed correlated color temperature the fixture is adjusted through dimming controls providing a lower intensity in the mornings and gradually transition to a higher intensity as the day progresses before decreasing again in the evening.
- Color tuning: This technique involves adjusting both the CCT and the light intensity to try to mimic daytime versus nighttime cycle. Cooler CCT (ranges from 4,000 Kelvin and up) are used during the day and warmer temperatures (3,500 Kelvin and lower) will mimic the sun rising and setting at appropriate times.
- Stimulus tuning: This lighting technology replaces the “bad blue” with “good blue” light wavelengths. These light fixtures can be programmed to reduce blue light wavelengths during nighttime to limit melatonin suppression.
When designing lighting systems for these types of structures, what design factors are being requested? Are there any particular technical advantages that are or need to be considered?
Luis Alvarez Colon: In patient rooms, giving the flexibility to the nurses and doctors on controlling several zones in multiples places is desired. For example, there are lighting controls entering the room that control the patient, visitor and work areas. At the patient area, there are lighting controls for nurses with the same capabilities as the controls at the entrance. Additionally, there are controls for the patients, if they wanted to have a reading or ambient light as well as controls for nightlights to prevent any accidents if they need to go to the bathroom.
LED lighting is seen more and more in health care, this is driven by requirements for lighting controls and efficiency. LED light fixtures are made to be dimmed. Also, the ability to change the color of a fixture if desired for specific use such as circadian rhythm, LED lighting can provide this and a lot of flexibility generally. They are low in power consumption compared to traditional fluorescent light fixtures.